The second ACTRIS inter-comparison (2016) for Aerosol Chemical Speciation Monitors (ACSM): Calibration protocols and instrument performance evaluations

Abstract

This work describes results obtained from the 2016 Aerosol Chemical Speciation Monitor (ACSM) intercomparison exercise performed at the Aerosol Chemical Monitor Calibration Center (ACMCC, France). Fifteen quadrupole ACSMs (Q_ACSM) from the European Research Infrastructure for the observation of Aerosols, Clouds and Trace gases (ACTRIS) network were calibrated using a new procedure that acquires calibration data under the same operating conditions as those used during sampling and hence gets information representative of instrument performance. The new calibration procedure notably resulted in a decrease in the spread of the measured sulfate mass concentrations, improving the reproducibility of inorganic species measurements between ACSMs as well as the consistency with co-located independent instruments. Tested calibration procedures also allowed for the investigation of artifacts in individual instruments, such as the overestimation of m/z 44 from organic aerosol. This effect was quantified by the m/z (mass-to-charge) 44 to nitrate ratio measured during ammonium nitrate calibrations, with values ranging from 0.03 to 0.26, showing that it can be significant for some instruments. The fragmentation table correction previously proposed to account for this artifact was applied to the measurements acquired during this study. For some instruments (those with high artifacts), this fragmentation table adjustment led to an "overcorrection" of the f44 (m/z 44/Org) signal. This correction based on measurements made with pure NH 4 NO 3 , assumes that the magnitude of the artifact is independent of chemical composition. Using data acquired at different NH 4 NO 3 mixing ratios (from solutions of NH 4 NO 3 and (NH 4) 2 SO 4) we observe that the magnitude of the artifact varies as a function of composition. Here we applied an updated correction, dependent on the ambient NO 3 mass fraction, which resulted in an improved agreement in organic signal among instruments. This work illustrates the benefits of integrating new calibration procedures and artifact corrections, but also highlights the benefits of these intercomparison exercises to continue to improve our knowledge of how these instruments operate, and assist us in interpreting atmospheric chemistry.

Orange Snow—A Saharan Dust Intrusion over Romania During Winter Conditions

“…The instrument, described in details by [45], is based on the vaporisation of particles under vacuum at approximately 600 • C, ionization, and then analyzed using a quadrupole mass spectrometer [46,47]. The ACSM data treatment have been done using the standard operational procedure developed by ACTRIS [48].…”

Long-term aerosol optical hygroscopicity study at the ACTRIS SIRTA observatory: synergy between ceilometer and in situ measurements

“…Most of the studies investigating the effect of aerosol hygroscopicity on aerosol optical properties have focused on the particle scattering coefficient (σ sp ) measured with in situ techniques (e.g., Covert et al, 1972;Sorooshian et al, 2008;Zieger et al, 2011;Titos et al, 2016). More recently, remote-sensing measurements have been used to investigate aerosol hygroscopicity using the particle extinction coefficient (Veselovskii, et al, 2009) and particle backscattering coefficient (Granados-Muñoz, et al, 2015;Fernández et al, 2018;Bedoya-Velásquez et al, 2018). These studies use the enhancement factor f ξ (RH) defined as follows:…”

“…Both ACSM and AE33 measurements are subject to AC-TRIS (http://www.actris.eu, last access: 25 May 2019) quality control and quality assurance procedures, notably par-ticipating in regular intercomparison exercises at the European Center for Aerosol Calibration (e.g., https://www. actris-ecac.eu/files/ECAC-report-AP-2017-4-2.pdf, last access: 25 May 2019; Crenn et al, 2015;Freney et al, 2019). A full description of the calibration and data treatment methods for both AE33 and ACSM used in the present study is presented by Petit et al (2017Petit et al ( , 2015.…”

“…This factor is defined as the ratio between the optical/microphysical property under certain RH conditions and the optical/microphysical property under dry conditions within the volume of atmosphere selected. These studies have been performed using in situ setups, such as humidrograph tandem nephelometers and the Humidified Tandem Differential Mobility Analyzer (HTDMA) (e.g., Hänel, 1976;Zieger et al, 2011;Titos et al, 2016) as well as remotesensing instrumentation (e.g., Pilinis and Pandis, 1995;Ferrare et al, 1998;Feingold and Morley, 2003;Veselovskii et al, 2009;Granados-Muñoz et al, 2015;Bedoya-Velásquez et al, 2018, and references therein). Regarding the in situ setups, there are studies such as Titos et al (2014a), Zhang et al (2015), and Zieger et al (2014) which deeply evaluate the hygroscopic growth properties and their relationship with organic and inorganic chemical composition, showing a decreasing tendency between f (RH) and organic aerosols (OA) and an increasing tendency between f (RH) and inorganic aerosols (IA), allowing us to evaluate the role of organic and inorganic aerosol in hygroscopic growth studies.…”

“…Remotesensing techniques are able to overcome this limitation since they examine particles directly in the atmosphere without any modification of the air sample. Previous remote-sensing studies have combined lidars and radiosonde measurements (e.g., Ferrare et al, 1998;Granados-Muñoz et al, 2015;Fernández et al, 2015) and Raman lidars and microwave radiometer (MWR) data (Navas-Guzmán et al, 2014;Bedoya-Velásquez et al, 2018) to investigate aerosol hygroscopic growth. Despite their promising capabilities, most of the lidar systems do not operate continuously due to the cost and maintenance requirements; thus, the number of hygroscopic growth cases explored is typically small (Vesolovskii et al, 2009;Granados-Muñoz et al, 2015;Fernández et al, 2018;Bedoya-Velásquez et al, 2018).…”